Here is a reach back to a series of posts I did almost three years ago, Sneaking in a Dungeon.
Since I run GURPS, and my players often use magic to augment their sneakiness, here are some rules and rulings. Be careful quoting them outside of my game, however - some of what is below is my interpretation. Check the page references to see what the rules actually say if you choose to use these.
Boots are -0 to Stealth; the rules assume fairly hard-soled footwear and give bonuses for soft gear. Sollerets are -2 to Stealth rolls versus Hearing, since they're assumed to be stiff and armored all around (even the soles have full DR.) Barefoot is a +1, like soft shoes, but remember that Tough Skin doesn't prevent the effects of contact agents, thorns, spikes, and other skin-affecting or skin-penetrating hazards.
Invisibility gives a +9 to Stealth where been seen would matter (per Invisibility, p. B63) This is to say, it's not automatica perfect stealth. By default, assume the Invisibility spell affects up to Heavy encumbrance.
Levitation and Flight do not include Stealth, Silence, or any other form of anti-detection. It will let you ignore any penalties to Stealth for noisy floors, however, and I also allow you to move up to your full levitating Move without incurring a -5 to Stealth for moving above Move 1 (per p. B222) against Hearing; same with gliding (and most magical flight.) However, the -5 will apply against creatures using Vibration Sense (Air) or other similar powers.
No-Smell removes any chance of Smell-based detection entirely; there is no roll. Normally, you don't roll Stealth for smell - for that, actually disguise your smell or move downwind of your foes.
Gesture is a quiet way to communicate, but you need to be in physical contact or able to see each other. If you can't see the person you are gesturing to, you can communicate only one way. You won't necessarily know you communicated (the person glanced away, misunderstood, is waiting for confirmation, can't see you after all, etc.) without reciprocal sight.
Distance Matters. Don't forget that distance from a target is a net bonus, and being close might cause your foe to notice you. (Editing later - to be more clear here - by "net bonus" I mean the sense rolls of any foe might be lowered by range. You will not get a bonus on your Stealth roll itself.)
Roll Once Against Everything. That is, roll once for Stealth against all forms of detection, and apply the penalties individually. Don't roll per sense. For example, Nakar is Invisible and rolls against his Stealth-12 and rolls a 9. A foe would need to win the contest by more than 12 for Vision and more than 3 for Hearing. Monsters hunting by Vibration Sense would need to win by more than 3, those by Detect Life wouldn't be affected by Stealth, and those hunting by smell would just need a normal Smell roll.
So the best way to sneak? Invisible Mage-Stealthed Ethereal Body No Smell, with Remove Aura tossed on so you don't seem to be alive. Still might not work, if a foe has Cosmic senses or See Invisible, but it's worth a try.